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<a class="jxr_linenumber" name="1" href="#1">1</a>   <em class="jxr_comment">/*</em>
<a class="jxr_linenumber" name="2" href="#2">2</a>   <em class="jxr_comment"> * Copyright 2012 The Netty Project</em>
<a class="jxr_linenumber" name="3" href="#3">3</a>   <em class="jxr_comment"> *</em>
<a class="jxr_linenumber" name="4" href="#4">4</a>   <em class="jxr_comment"> * The Netty Project licenses this file to you under the Apache License,</em>
<a class="jxr_linenumber" name="5" href="#5">5</a>   <em class="jxr_comment"> * version 2.0 (the "License"); you may not use this file except in compliance</em>
<a class="jxr_linenumber" name="6" href="#6">6</a>   <em class="jxr_comment"> * with the License. You may obtain a copy of the License at:</em>
<a class="jxr_linenumber" name="7" href="#7">7</a>   <em class="jxr_comment"> *</em>
<a class="jxr_linenumber" name="8" href="#8">8</a>   <em class="jxr_comment"> *   <a href="http://www.apache.org/licenses/LICENSE-2.0" target="alexandria_uri">http://www.apache.org/licenses/LICENSE-2.0</a></em>
<a class="jxr_linenumber" name="9" href="#9">9</a>   <em class="jxr_comment"> *</em>
<a class="jxr_linenumber" name="10" href="#10">10</a>  <em class="jxr_comment"> * Unless required by applicable law or agreed to in writing, software</em>
<a class="jxr_linenumber" name="11" href="#11">11</a>  <em class="jxr_comment"> * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT</em>
<a class="jxr_linenumber" name="12" href="#12">12</a>  <em class="jxr_comment"> * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the</em>
<a class="jxr_linenumber" name="13" href="#13">13</a>  <em class="jxr_comment"> * License for the specific language governing permissions and limitations</em>
<a class="jxr_linenumber" name="14" href="#14">14</a>  <em class="jxr_comment"> * under the License.</em>
<a class="jxr_linenumber" name="15" href="#15">15</a>  <em class="jxr_comment"> */</em>
<a class="jxr_linenumber" name="16" href="#16">16</a>  <strong class="jxr_keyword">package</strong> org.jboss.netty.channel;
<a class="jxr_linenumber" name="17" href="#17">17</a>  
<a class="jxr_linenumber" name="18" href="#18">18</a>  <strong class="jxr_keyword">import</strong> org.jboss.netty.bootstrap.Bootstrap;
<a class="jxr_linenumber" name="19" href="#19">19</a>  <strong class="jxr_keyword">import</strong> org.jboss.netty.channel.group.ChannelGroup;
<a class="jxr_linenumber" name="20" href="#20">20</a>  
<a class="jxr_linenumber" name="21" href="#21">21</a>  <strong class="jxr_keyword">import</strong> java.lang.annotation.Documented;
<a class="jxr_linenumber" name="22" href="#22">22</a>  <strong class="jxr_keyword">import</strong> java.lang.annotation.ElementType;
<a class="jxr_linenumber" name="23" href="#23">23</a>  <strong class="jxr_keyword">import</strong> java.lang.annotation.Inherited;
<a class="jxr_linenumber" name="24" href="#24">24</a>  <strong class="jxr_keyword">import</strong> java.lang.annotation.Retention;
<a class="jxr_linenumber" name="25" href="#25">25</a>  <strong class="jxr_keyword">import</strong> java.lang.annotation.RetentionPolicy;
<a class="jxr_linenumber" name="26" href="#26">26</a>  <strong class="jxr_keyword">import</strong> java.lang.annotation.Target;
<a class="jxr_linenumber" name="27" href="#27">27</a>  
<a class="jxr_linenumber" name="28" href="#28">28</a>  <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="29" href="#29">29</a>  <em class="jxr_javadoccomment"> * Handles or intercepts a {@link ChannelEvent}, and sends a</em>
<a class="jxr_linenumber" name="30" href="#30">30</a>  <em class="jxr_javadoccomment"> * {@link ChannelEvent} to the next handler in a {@link ChannelPipeline}.</em>
<a class="jxr_linenumber" name="31" href="#31">31</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="32" href="#32">32</a>  <em class="jxr_javadoccomment"> * &lt;h3&gt;Sub-types&lt;/h3&gt;</em>
<a class="jxr_linenumber" name="33" href="#33">33</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="34" href="#34">34</a>  <em class="jxr_javadoccomment"> * {@link ChannelHandler} itself does not provide any method.  To handle a</em>
<a class="jxr_linenumber" name="35" href="#35">35</a>  <em class="jxr_javadoccomment"> * {@link ChannelEvent} you need to implement its sub-interfaces.  There are</em>
<a class="jxr_linenumber" name="36" href="#36">36</a>  <em class="jxr_javadoccomment"> * two sub-interfaces which handles a received event, one for upstream events</em>
<a class="jxr_linenumber" name="37" href="#37">37</a>  <em class="jxr_javadoccomment"> * and the other for downstream events:</em>
<a class="jxr_linenumber" name="38" href="#38">38</a>  <em class="jxr_javadoccomment"> * &lt;ul&gt;</em>
<a class="jxr_linenumber" name="39" href="#39">39</a>  <em class="jxr_javadoccomment"> * &lt;li&gt;{@link ChannelUpstreamHandler} handles and intercepts an upstream {@link ChannelEvent}.&lt;/li&gt;</em>
<a class="jxr_linenumber" name="40" href="#40">40</a>  <em class="jxr_javadoccomment"> * &lt;li&gt;{@link ChannelDownstreamHandler} handles and intercepts a downstream {@link ChannelEvent}.&lt;/li&gt;</em>
<a class="jxr_linenumber" name="41" href="#41">41</a>  <em class="jxr_javadoccomment"> * &lt;/ul&gt;</em>
<a class="jxr_linenumber" name="42" href="#42">42</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="43" href="#43">43</a>  <em class="jxr_javadoccomment"> * You will also find more detailed explanation from the documentation of</em>
<a class="jxr_linenumber" name="44" href="#44">44</a>  <em class="jxr_javadoccomment"> * each sub-interface on how an event is interpreted when it goes upstream and</em>
<a class="jxr_linenumber" name="45" href="#45">45</a>  <em class="jxr_javadoccomment"> * downstream respectively.</em>
<a class="jxr_linenumber" name="46" href="#46">46</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="47" href="#47">47</a>  <em class="jxr_javadoccomment"> * &lt;h3&gt;The context object&lt;/h3&gt;</em>
<a class="jxr_linenumber" name="48" href="#48">48</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="49" href="#49">49</a>  <em class="jxr_javadoccomment"> * A {@link ChannelHandler} is provided with a {@link ChannelHandlerContext}</em>
<a class="jxr_linenumber" name="50" href="#50">50</a>  <em class="jxr_javadoccomment"> * object.  A {@link ChannelHandler} is supposed to interact with the</em>
<a class="jxr_linenumber" name="51" href="#51">51</a>  <em class="jxr_javadoccomment"> * {@link ChannelPipeline} it belongs to via a context object.  Using the</em>
<a class="jxr_linenumber" name="52" href="#52">52</a>  <em class="jxr_javadoccomment"> * context object, the {@link ChannelHandler} can pass events upstream or</em>
<a class="jxr_linenumber" name="53" href="#53">53</a>  <em class="jxr_javadoccomment"> * downstream, modify the pipeline dynamically, or store the information</em>
<a class="jxr_linenumber" name="54" href="#54">54</a>  <em class="jxr_javadoccomment"> * (attachment) which is specific to the handler.</em>
<a class="jxr_linenumber" name="55" href="#55">55</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="56" href="#56">56</a>  <em class="jxr_javadoccomment"> * &lt;h3&gt;State management&lt;/h3&gt;</em>
<a class="jxr_linenumber" name="57" href="#57">57</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="58" href="#58">58</a>  <em class="jxr_javadoccomment"> * A {@link ChannelHandler} often needs to store some stateful information.</em>
<a class="jxr_linenumber" name="59" href="#59">59</a>  <em class="jxr_javadoccomment"> * The simplest and recommended approach is to use member variables:</em>
<a class="jxr_linenumber" name="60" href="#60">60</a>  <em class="jxr_javadoccomment"> * &lt;pre&gt;</em>
<a class="jxr_linenumber" name="61" href="#61">61</a>  <em class="jxr_javadoccomment"> * public class DataServerHandler extends {@link SimpleChannelHandler} {</em>
<a class="jxr_linenumber" name="62" href="#62">62</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="63" href="#63">63</a>  <em class="jxr_javadoccomment"> *     &lt;b&gt;private boolean loggedIn;&lt;/b&gt;</em>
<a class="jxr_linenumber" name="64" href="#64">64</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="65" href="#65">65</a>  <em class="jxr_javadoccomment"> *     {@code @Override}</em>
<a class="jxr_linenumber" name="66" href="#66">66</a>  <em class="jxr_javadoccomment"> *     public void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {</em>
<a class="jxr_linenumber" name="67" href="#67">67</a>  <em class="jxr_javadoccomment"> *         {@link Channel} ch = e.getChannel();</em>
<a class="jxr_linenumber" name="68" href="#68">68</a>  <em class="jxr_javadoccomment"> *         Object o = e.getMessage();</em>
<a class="jxr_linenumber" name="69" href="#69">69</a>  <em class="jxr_javadoccomment"> *         if (o instanceof LoginMessage) {</em>
<a class="jxr_linenumber" name="70" href="#70">70</a>  <em class="jxr_javadoccomment"> *             authenticate((LoginMessage) o);</em>
<a class="jxr_linenumber" name="71" href="#71">71</a>  <em class="jxr_javadoccomment"> *             &lt;b&gt;loggedIn = true;&lt;/b&gt;</em>
<a class="jxr_linenumber" name="72" href="#72">72</a>  <em class="jxr_javadoccomment"> *         } else (o instanceof GetDataMessage) {</em>
<a class="jxr_linenumber" name="73" href="#73">73</a>  <em class="jxr_javadoccomment"> *             if (&lt;b&gt;loggedIn&lt;/b&gt;) {</em>
<a class="jxr_linenumber" name="74" href="#74">74</a>  <em class="jxr_javadoccomment"> *                 ch.write(fetchSecret((GetDataMessage) o));</em>
<a class="jxr_linenumber" name="75" href="#75">75</a>  <em class="jxr_javadoccomment"> *             } else {</em>
<a class="jxr_linenumber" name="76" href="#76">76</a>  <em class="jxr_javadoccomment"> *                 fail();</em>
<a class="jxr_linenumber" name="77" href="#77">77</a>  <em class="jxr_javadoccomment"> *             }</em>
<a class="jxr_linenumber" name="78" href="#78">78</a>  <em class="jxr_javadoccomment"> *         }</em>
<a class="jxr_linenumber" name="79" href="#79">79</a>  <em class="jxr_javadoccomment"> *     }</em>
<a class="jxr_linenumber" name="80" href="#80">80</a>  <em class="jxr_javadoccomment"> *     ...</em>
<a class="jxr_linenumber" name="81" href="#81">81</a>  <em class="jxr_javadoccomment"> * }</em>
<a class="jxr_linenumber" name="82" href="#82">82</a>  <em class="jxr_javadoccomment"> * &lt;/pre&gt;</em>
<a class="jxr_linenumber" name="83" href="#83">83</a>  <em class="jxr_javadoccomment"> * Because the handler instance has a state variable which is dedicated to</em>
<a class="jxr_linenumber" name="84" href="#84">84</a>  <em class="jxr_javadoccomment"> * one connection, you have to create a new handler instance for each new</em>
<a class="jxr_linenumber" name="85" href="#85">85</a>  <em class="jxr_javadoccomment"> * channel to avoid a race condition where a unauthenticated client can get</em>
<a class="jxr_linenumber" name="86" href="#86">86</a>  <em class="jxr_javadoccomment"> * the confidential information:</em>
<a class="jxr_linenumber" name="87" href="#87">87</a>  <em class="jxr_javadoccomment"> * &lt;pre&gt;</em>
<a class="jxr_linenumber" name="88" href="#88">88</a>  <em class="jxr_javadoccomment"> * // Create a new handler instance per channel.</em>
<a class="jxr_linenumber" name="89" href="#89">89</a>  <em class="jxr_javadoccomment"> * // See {@link Bootstrap#setPipelineFactory(ChannelPipelineFactory)}.</em>
<a class="jxr_linenumber" name="90" href="#90">90</a>  <em class="jxr_javadoccomment"> * public class DataServerPipelineFactory implements {@link ChannelPipelineFactory} {</em>
<a class="jxr_linenumber" name="91" href="#91">91</a>  <em class="jxr_javadoccomment"> *     public {@link ChannelPipeline} getPipeline() {</em>
<a class="jxr_linenumber" name="92" href="#92">92</a>  <em class="jxr_javadoccomment"> *         return {@link Channels}.pipeline(&lt;b&gt;new DataServerHandler()&lt;/b&gt;);</em>
<a class="jxr_linenumber" name="93" href="#93">93</a>  <em class="jxr_javadoccomment"> *     }</em>
<a class="jxr_linenumber" name="94" href="#94">94</a>  <em class="jxr_javadoccomment"> * }</em>
<a class="jxr_linenumber" name="95" href="#95">95</a>  <em class="jxr_javadoccomment"> * &lt;/pre&gt;</em>
<a class="jxr_linenumber" name="96" href="#96">96</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="97" href="#97">97</a>  <em class="jxr_javadoccomment"> * &lt;h4&gt;Using an attachment&lt;/h4&gt;</em>
<a class="jxr_linenumber" name="98" href="#98">98</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="99" href="#99">99</a>  <em class="jxr_javadoccomment"> * Although it's recommended to use member variables to store the state of a</em>
<a class="jxr_linenumber" name="100" href="#100">100</a> <em class="jxr_javadoccomment"> * handler, for some reason you might not want to create many handler instances.</em>
<a class="jxr_linenumber" name="101" href="#101">101</a> <em class="jxr_javadoccomment"> * In such a case, you can use an &lt;em&gt;attachment&lt;/em&gt; which is provided by</em>
<a class="jxr_linenumber" name="102" href="#102">102</a> <em class="jxr_javadoccomment"> * {@link ChannelHandlerContext}:</em>
<a class="jxr_linenumber" name="103" href="#103">103</a> <em class="jxr_javadoccomment"> * &lt;pre&gt;</em>
<a class="jxr_linenumber" name="104" href="#104">104</a> <em class="jxr_javadoccomment"> * {@code @Sharable}</em>
<a class="jxr_linenumber" name="105" href="#105">105</a> <em class="jxr_javadoccomment"> * public class DataServerHandler extends {@link SimpleChannelHandler} {</em>
<a class="jxr_linenumber" name="106" href="#106">106</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="107" href="#107">107</a> <em class="jxr_javadoccomment"> *     {@code @Override}</em>
<a class="jxr_linenumber" name="108" href="#108">108</a> <em class="jxr_javadoccomment"> *     public void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {</em>
<a class="jxr_linenumber" name="109" href="#109">109</a> <em class="jxr_javadoccomment"> *         {@link Channel} ch = e.getChannel();</em>
<a class="jxr_linenumber" name="110" href="#110">110</a> <em class="jxr_javadoccomment"> *         Object o = e.getMessage();</em>
<a class="jxr_linenumber" name="111" href="#111">111</a> <em class="jxr_javadoccomment"> *         if (o instanceof LoginMessage) {</em>
<a class="jxr_linenumber" name="112" href="#112">112</a> <em class="jxr_javadoccomment"> *             authenticate((LoginMessage) o);</em>
<a class="jxr_linenumber" name="113" href="#113">113</a> <em class="jxr_javadoccomment"> *             &lt;b&gt;ctx.setAttachment(true)&lt;/b&gt;;</em>
<a class="jxr_linenumber" name="114" href="#114">114</a> <em class="jxr_javadoccomment"> *         } else (o instanceof GetDataMessage) {</em>
<a class="jxr_linenumber" name="115" href="#115">115</a> <em class="jxr_javadoccomment"> *             if (&lt;b&gt;Boolean.TRUE.equals(ctx.getAttachment())&lt;/b&gt;) {</em>
<a class="jxr_linenumber" name="116" href="#116">116</a> <em class="jxr_javadoccomment"> *                 ch.write(fetchSecret((GetDataMessage) o));</em>
<a class="jxr_linenumber" name="117" href="#117">117</a> <em class="jxr_javadoccomment"> *             } else {</em>
<a class="jxr_linenumber" name="118" href="#118">118</a> <em class="jxr_javadoccomment"> *                 fail();</em>
<a class="jxr_linenumber" name="119" href="#119">119</a> <em class="jxr_javadoccomment"> *             }</em>
<a class="jxr_linenumber" name="120" href="#120">120</a> <em class="jxr_javadoccomment"> *         }</em>
<a class="jxr_linenumber" name="121" href="#121">121</a> <em class="jxr_javadoccomment"> *     }</em>
<a class="jxr_linenumber" name="122" href="#122">122</a> <em class="jxr_javadoccomment"> *     ...</em>
<a class="jxr_linenumber" name="123" href="#123">123</a> <em class="jxr_javadoccomment"> * }</em>
<a class="jxr_linenumber" name="124" href="#124">124</a> <em class="jxr_javadoccomment"> * &lt;/pre&gt;</em>
<a class="jxr_linenumber" name="125" href="#125">125</a> <em class="jxr_javadoccomment"> * Now that the state of the handler is stored as an attachment, you can add the</em>
<a class="jxr_linenumber" name="126" href="#126">126</a> <em class="jxr_javadoccomment"> * same handler instance to different pipelines:</em>
<a class="jxr_linenumber" name="127" href="#127">127</a> <em class="jxr_javadoccomment"> * &lt;pre&gt;</em>
<a class="jxr_linenumber" name="128" href="#128">128</a> <em class="jxr_javadoccomment"> * public class DataServerPipelineFactory implements {@link ChannelPipelineFactory} {</em>
<a class="jxr_linenumber" name="129" href="#129">129</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="130" href="#130">130</a> <em class="jxr_javadoccomment"> *     private static final DataServerHandler &lt;b&gt;SHARED&lt;/b&gt; = new DataServerHandler();</em>
<a class="jxr_linenumber" name="131" href="#131">131</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="132" href="#132">132</a> <em class="jxr_javadoccomment"> *     public {@link ChannelPipeline} getPipeline() {</em>
<a class="jxr_linenumber" name="133" href="#133">133</a> <em class="jxr_javadoccomment"> *         return {@link Channels}.pipeline(&lt;b&gt;SHARED&lt;/b&gt;);</em>
<a class="jxr_linenumber" name="134" href="#134">134</a> <em class="jxr_javadoccomment"> *     }</em>
<a class="jxr_linenumber" name="135" href="#135">135</a> <em class="jxr_javadoccomment"> * }</em>
<a class="jxr_linenumber" name="136" href="#136">136</a> <em class="jxr_javadoccomment"> * &lt;/pre&gt;</em>
<a class="jxr_linenumber" name="137" href="#137">137</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="138" href="#138">138</a> <em class="jxr_javadoccomment"> * &lt;h4&gt;Using a {@link ChannelLocal}&lt;/h4&gt;</em>
<a class="jxr_linenumber" name="139" href="#139">139</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="140" href="#140">140</a> <em class="jxr_javadoccomment"> * If you have a state variable which needs to be accessed either from other</em>
<a class="jxr_linenumber" name="141" href="#141">141</a> <em class="jxr_javadoccomment"> * handlers or outside handlers, you can use {@link ChannelLocal}:</em>
<a class="jxr_linenumber" name="142" href="#142">142</a> <em class="jxr_javadoccomment"> * &lt;pre&gt;</em>
<a class="jxr_linenumber" name="143" href="#143">143</a> <em class="jxr_javadoccomment"> * public final class DataServerState {</em>
<a class="jxr_linenumber" name="144" href="#144">144</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="145" href="#145">145</a> <em class="jxr_javadoccomment"> *     &lt;b&gt;public static final {@link ChannelLocal}&amp;lt;Boolean&amp;gt; loggedIn = new {@link ChannelLocal}&amp;lt;&amp;gt;() {</em>
<a class="jxr_linenumber" name="146" href="#146">146</a> <em class="jxr_javadoccomment"> *         protected Boolean initialValue(Channel channel) {</em>
<a class="jxr_linenumber" name="147" href="#147">147</a> <em class="jxr_javadoccomment"> *             return false;</em>
<a class="jxr_linenumber" name="148" href="#148">148</a> <em class="jxr_javadoccomment"> *         }</em>
<a class="jxr_linenumber" name="149" href="#149">149</a> <em class="jxr_javadoccomment"> *     }&lt;/b&gt;</em>
<a class="jxr_linenumber" name="150" href="#150">150</a> <em class="jxr_javadoccomment"> *     ...</em>
<a class="jxr_linenumber" name="151" href="#151">151</a> <em class="jxr_javadoccomment"> * }</em>
<a class="jxr_linenumber" name="152" href="#152">152</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="153" href="#153">153</a> <em class="jxr_javadoccomment"> * {@code @Sharable}</em>
<a class="jxr_linenumber" name="154" href="#154">154</a> <em class="jxr_javadoccomment"> * public class DataServerHandler extends {@link SimpleChannelHandler} {</em>
<a class="jxr_linenumber" name="155" href="#155">155</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="156" href="#156">156</a> <em class="jxr_javadoccomment"> *     {@code @Override}</em>
<a class="jxr_linenumber" name="157" href="#157">157</a> <em class="jxr_javadoccomment"> *     public void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {</em>
<a class="jxr_linenumber" name="158" href="#158">158</a> <em class="jxr_javadoccomment"> *         Channel ch = e.getChannel();</em>
<a class="jxr_linenumber" name="159" href="#159">159</a> <em class="jxr_javadoccomment"> *         Object o = e.getMessage();</em>
<a class="jxr_linenumber" name="160" href="#160">160</a> <em class="jxr_javadoccomment"> *         if (o instanceof LoginMessage) {</em>
<a class="jxr_linenumber" name="161" href="#161">161</a> <em class="jxr_javadoccomment"> *             authenticate((LoginMessage) o);</em>
<a class="jxr_linenumber" name="162" href="#162">162</a> <em class="jxr_javadoccomment"> *             &lt;b&gt;DataServerState.loggedIn.set(ch, true);&lt;/b&gt;</em>
<a class="jxr_linenumber" name="163" href="#163">163</a> <em class="jxr_javadoccomment"> *         } else (o instanceof GetDataMessage) {</em>
<a class="jxr_linenumber" name="164" href="#164">164</a> <em class="jxr_javadoccomment"> *             if (&lt;b&gt;DataServerState.loggedIn.get(ch)&lt;/b&gt;) {</em>
<a class="jxr_linenumber" name="165" href="#165">165</a> <em class="jxr_javadoccomment"> *                 ctx.getChannel().write(fetchSecret((GetDataMessage) o));</em>
<a class="jxr_linenumber" name="166" href="#166">166</a> <em class="jxr_javadoccomment"> *             } else {</em>
<a class="jxr_linenumber" name="167" href="#167">167</a> <em class="jxr_javadoccomment"> *                 fail();</em>
<a class="jxr_linenumber" name="168" href="#168">168</a> <em class="jxr_javadoccomment"> *             }</em>
<a class="jxr_linenumber" name="169" href="#169">169</a> <em class="jxr_javadoccomment"> *         }</em>
<a class="jxr_linenumber" name="170" href="#170">170</a> <em class="jxr_javadoccomment"> *     }</em>
<a class="jxr_linenumber" name="171" href="#171">171</a> <em class="jxr_javadoccomment"> *     ...</em>
<a class="jxr_linenumber" name="172" href="#172">172</a> <em class="jxr_javadoccomment"> * }</em>
<a class="jxr_linenumber" name="173" href="#173">173</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="174" href="#174">174</a> <em class="jxr_javadoccomment"> * // Print the remote addresses of the authenticated clients:</em>
<a class="jxr_linenumber" name="175" href="#175">175</a> <em class="jxr_javadoccomment"> * {@link ChannelGroup} allClientChannels = ...;</em>
<a class="jxr_linenumber" name="176" href="#176">176</a> <em class="jxr_javadoccomment"> * for ({@link Channel} ch: allClientChannels) {</em>
<a class="jxr_linenumber" name="177" href="#177">177</a> <em class="jxr_javadoccomment"> *     if (&lt;b&gt;DataServerState.loggedIn.get(ch)&lt;/b&gt;) {</em>
<a class="jxr_linenumber" name="178" href="#178">178</a> <em class="jxr_javadoccomment"> *         System.out.println(ch.getRemoteAddress());</em>
<a class="jxr_linenumber" name="179" href="#179">179</a> <em class="jxr_javadoccomment"> *     }</em>
<a class="jxr_linenumber" name="180" href="#180">180</a> <em class="jxr_javadoccomment"> * }</em>
<a class="jxr_linenumber" name="181" href="#181">181</a> <em class="jxr_javadoccomment"> * &lt;/pre&gt;</em>
<a class="jxr_linenumber" name="182" href="#182">182</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="183" href="#183">183</a> <em class="jxr_javadoccomment"> * &lt;h4&gt;The {@code @Sharable} annotation&lt;/h4&gt;</em>
<a class="jxr_linenumber" name="184" href="#184">184</a> <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="185" href="#185">185</a> <em class="jxr_javadoccomment"> * In the examples above which used an attachment or a {@link ChannelLocal},</em>
<a class="jxr_linenumber" name="186" href="#186">186</a> <em class="jxr_javadoccomment"> * you might have noticed the {@code @Sharable} annotation.</em>
<a class="jxr_linenumber" name="187" href="#187">187</a> <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="188" href="#188">188</a> <em class="jxr_javadoccomment"> * If a {@link ChannelHandler} is annotated with the {@code @Sharable}</em>
<a class="jxr_linenumber" name="189" href="#189">189</a> <em class="jxr_javadoccomment"> * annotation, it means you can create an instance of the handler just once and</em>
<a class="jxr_linenumber" name="190" href="#190">190</a> <em class="jxr_javadoccomment"> * add it to one or more {@link ChannelPipeline}s multiple times without</em>
<a class="jxr_linenumber" name="191" href="#191">191</a> <em class="jxr_javadoccomment"> * a race condition.</em>
<a class="jxr_linenumber" name="192" href="#192">192</a> <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="193" href="#193">193</a> <em class="jxr_javadoccomment"> * If this annotation is not specified, you have to create a new handler</em>
<a class="jxr_linenumber" name="194" href="#194">194</a> <em class="jxr_javadoccomment"> * instance every time you add it to a pipeline because it has unshared state</em>
<a class="jxr_linenumber" name="195" href="#195">195</a> <em class="jxr_javadoccomment"> * such as member variables.</em>
<a class="jxr_linenumber" name="196" href="#196">196</a> <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="197" href="#197">197</a> <em class="jxr_javadoccomment"> * This annotation is provided for documentation purpose, just like</em>
<a class="jxr_linenumber" name="198" href="#198">198</a> <em class="jxr_javadoccomment"> * &lt;a href="<a href="http://www.javaconcurrencyinpractice.com/annotations/doc/" target="alexandria_uri">http://www.javaconcurrencyinpractice.com/annotations/doc/</a>"&gt;the JCIP annotations&lt;/a&gt;.</em>
<a class="jxr_linenumber" name="199" href="#199">199</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="200" href="#200">200</a> <em class="jxr_javadoccomment"> * &lt;h3&gt;Additional resources worth reading&lt;/h3&gt;</em>
<a class="jxr_linenumber" name="201" href="#201">201</a> <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="202" href="#202">202</a> <em class="jxr_javadoccomment"> * Please refer to the {@link ChannelEvent} and {@link ChannelPipeline} to find</em>
<a class="jxr_linenumber" name="203" href="#203">203</a> <em class="jxr_javadoccomment"> * out what a upstream event and a downstream event are, what fundamental</em>
<a class="jxr_linenumber" name="204" href="#204">204</a> <em class="jxr_javadoccomment"> * differences they have, and how they flow in a pipeline.</em>
<a class="jxr_linenumber" name="205" href="#205">205</a> <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="206" href="#206">206</a> <em class="jxr_javadoccomment"> * @apiviz.landmark</em>
<a class="jxr_linenumber" name="207" href="#207">207</a> <em class="jxr_javadoccomment"> * @apiviz.exclude ^org\.jboss\.netty\.handler\..*$</em>
<a class="jxr_linenumber" name="208" href="#208">208</a> <em class="jxr_javadoccomment"> */</em>
<a class="jxr_linenumber" name="209" href="#209">209</a> <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">interface</strong> <a href="../../../../org/jboss/netty/channel/ChannelHandler.html">ChannelHandler</a> {
<a class="jxr_linenumber" name="210" href="#210">210</a> 
<a class="jxr_linenumber" name="211" href="#211">211</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="212" href="#212">212</a> <em class="jxr_javadoccomment">     * Indicates that the same instance of the annotated {@link ChannelHandler}</em>
<a class="jxr_linenumber" name="213" href="#213">213</a> <em class="jxr_javadoccomment">     * can be added to one or more {@link ChannelPipeline}s multiple times</em>
<a class="jxr_linenumber" name="214" href="#214">214</a> <em class="jxr_javadoccomment">     * without a race condition.</em>
<a class="jxr_linenumber" name="215" href="#215">215</a> <em class="jxr_javadoccomment">     * &lt;p&gt;</em>
<a class="jxr_linenumber" name="216" href="#216">216</a> <em class="jxr_javadoccomment">     * If this annotation is not specified, you have to create a new handler</em>
<a class="jxr_linenumber" name="217" href="#217">217</a> <em class="jxr_javadoccomment">     * instance every time you add it to a pipeline because it has unshared</em>
<a class="jxr_linenumber" name="218" href="#218">218</a> <em class="jxr_javadoccomment">     * state such as member variables.</em>
<a class="jxr_linenumber" name="219" href="#219">219</a> <em class="jxr_javadoccomment">     * &lt;p&gt;</em>
<a class="jxr_linenumber" name="220" href="#220">220</a> <em class="jxr_javadoccomment">     * This annotation is provided for documentation purpose, just like</em>
<a class="jxr_linenumber" name="221" href="#221">221</a> <em class="jxr_javadoccomment">     * &lt;a href="<a href="http://www.javaconcurrencyinpractice.com/annotations/doc/" target="alexandria_uri">http://www.javaconcurrencyinpractice.com/annotations/doc/</a>"&gt;the JCIP annotations&lt;/a&gt;.</em>
<a class="jxr_linenumber" name="222" href="#222">222</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="223" href="#223">223</a>     @Inherited
<a class="jxr_linenumber" name="224" href="#224">224</a>     @Documented
<a class="jxr_linenumber" name="225" href="#225">225</a>     @Target(ElementType.TYPE)
<a class="jxr_linenumber" name="226" href="#226">226</a>     @Retention(RetentionPolicy.RUNTIME)
<a class="jxr_linenumber" name="227" href="#227">227</a>     @<strong class="jxr_keyword">interface</strong> <a href="../../../../org/jboss/netty/channel/ChannelHandler.html">Sharable</a> {
<a class="jxr_linenumber" name="228" href="#228">228</a>         <em class="jxr_comment">// no value</em>
<a class="jxr_linenumber" name="229" href="#229">229</a>     }
<a class="jxr_linenumber" name="230" href="#230">230</a> }
</pre>
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